selve: make 'shelve --interactive' not experimental

It is safe to do as 'shelve -i' uses the same code path as 'commit -i' that is
not experimental.

hgext/shelve.py

@@ -672,8 +672,7 b' def unshelve(ui, repo, *shelved, **opts)'
           ('p', 'patch', None,
            _('show patch')),
           ('i', 'interactive', None,
-           _('interactive mode, only works while creating a shelve'
-                   '(EXPERIMENTAL)')),
+           _('interactive mode, only works while creating a shelve')),
           ('', 'stat', None,
            _('output diffstat-style summary of changes'))] + commands.walkopts,
          _('hg shelve [OPTION]... [FILE]...'))

tests/test-shelve.t

@@ -60,6 +60,7 b' shelve has a help message'
    -m --message TEXT        use text as shelve message
    -n --name NAME           use the given name for the shelved commit
    -p --patch               show patch
+   -i --interactive         interactive mode, only works while creating a shelve
       --stat                output diffstat-style summary of changes
    -I --include PATTERN [+] include names matching the given patterns
    -X --exclude PATTERN [+] exclude names matching the given patterns